Exclusive footage from the new Terminator film has been revealed to thousands of attendees of a comics convention.

Terminator: Salvation is set to be released in 2009 and sees Christian Bale - star of The Dark Knight - as John Connor, leader of the human resistance against a robot uprising.

And director McG - who helmed both Charlie's Angels films - has previewed footage from the new film to receptive film lovers at the Comic-Con event in San Diego, California.

"We knew we were facing a challenge of credibility," he told an initially sceptical audience.

"It's the privilege of the audience to say, 'Hey, I don't know about this. I don't know about this McG guy. I don't know what their intentions are with this movie'.

"So I wanted to protect the movie and protect all of you by hiring the most credible actor of his generation: Christian Bale."

The director - who executive-produced The OC - told fans the new Terminator film had been written by Jonah Nolan, who co-wrote the screenplay for The Dark Knight with his brother Christopher.

And after telling the crowd he had consulted James Cameron - who directed the first two Terminator films - and the franchise's previous star Arnold Schwarzenegger, McG explained that he did not intend to water down the mythology of the franchise.

"We're shooting the picture with the picture first at all times," he was quoted by Empire as saying.

"I know there's been some talk about a PG-13 rating. Something I guaranteed Christian is that we put the picture first at all times.

"And I've been given [the studio's] blessing to make the picture and if it's a rated R picture it's a rated R picture and that's that."